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November 2014 • The PCB Magazine 53 paradox is that none of us would accept 99% in our personal lives, so why do we accept it in our businesses? Figure 1 shows what life would look like if we settled for having things right only 99% of the time in some areas we can all relate to. This kind of changes the perception that 99% is good enough, doesn't it? Contrast this with a six sigma level in which your local weatherperson's forecast would be correct every single day for 795 years in a row! What is Six Sigma? Sigma (σ) is the eighteenth letter in the Greek alphabet, and is defined and used in two different ways: 1) As a mathematical measure of the amount of variation in a process. This is normally re- ferred to as the standard deviation of a process; the lower the standard deviation, the better, and 2) To describe the quantity of defects a pro- cess will produce. This is normally referred to as the sigma level of a process and is a measure of process performance; the higher the sigma level, the better. Although statistics are usually associated with six sigma, that is only part of it; six sigma is the problem solving methodol- ogy called DMAIC (define, measure, analyze, improve, control). DMAIC is process that uses a collection of tools to identify, analyze, and eliminate sources of variation in a process. Six sigma can be an intimidating concept to grasp, particularly regarding the statistics and math part of the process. The key takeaway is that to achieve a six sigma level, process variation must be cut in half from a three sigma level. This concept will be explained in greater de- tail in the next issue, Best Practices 101: Part 5. PCB steve williams is the president of steve williams Consulting llC and the former strategic sourcing manager for Plexus Corp. he is the author of the books, Quality 101 handbook and survival is not mandato- ry: 10 things every Ceo should Know about lean. to read past columns, or to contact williams, click here. BEST PRACTICES 101, PART 4 continues Graphene is a two-dimensional material with extraordinary electronic and magnetic properties that can be tailored by cutting large sheets of the material down to ribbons of specific lengths and edge configurations. scientists have theorized that nanoribbons with zigzag edges are the most magnetic, making them suitable for spintronics applications. but this "top-down" fabrica - tion approach is not yet practical, because current lithographic tech- niques for tailoring the ribbons al- ways produce defects. now, scientists from uCla and tohoku university have discov- ered a new self-assembly method for producing defect-free graphene nanoribbons with periodic zigzag-edge regions. in this "bot- tom-up" technique, researchers use a copper sub- strate's unique properties to change the way the precursor molecules react to one another as they assemble into graphene nanoribbons. this allows the scientists to control the nanoribbons' length, edge configuration and location on the substrate. this new method is a stepping stone toward the production of self-assembled graphene de - vices that will vastly improve the performance of data storage circuits, batteries and electronics. Paul weiss, a member of uCla's California nanosystems institute, developed the method for producing the na- noribbons with Patrick han and taro hitosugi, professors at the advanced institute of materials re- search at tohoku university in sen- dai, Japan. the report appears in the journal aCs nano. Graphene Nanoribbons to Revolutionize Electronics